Amassing seniority and keeping plenty of members in the party in power are two of the most important things a state can do to bulk up its influence in Congress.

Both have been difficult feats for plenty of states recently, given the shift of House control in 2010, the reapportionment and redistricting that soon followed and the much-higher-than-normal departure of 28 senators in the past two elections.

Which is why it’s not a real surprise that this year’s Roll Call Clout Index shows a significant scrambling of the pecking order since Barack Obama’s presidency began in 2009. Some states are seeing surges in their potential for influence, while others are looking at throw weights in precipitous decline.

As mentioned in this space recently, the sudden ascent of Louisiana — which now has the fourth-most-potent delegation after finishing in the low 30s in the previous two studies — was central to the story of the year, which is that the Gulf Coast region has more collective power than any other region. Meanwhile, Massachusetts, which for two decades had routinely finished in the top 10, slipped down to 20th just as the Boston Marathon bombings were putting the state in the national spotlight.

But those delegations were hardly alone in seeing reversals of fortune in the past four years. In part because of generational turnovers in their delegations, four other states besides Massachusetts have seen their spots in the rankings drop by double digits between 2009 and this spring, while new positions of power and surges in federal spending have caused three other states besides Louisiana to jump more than 10 positions.

Having one of last year’s candidates for vice president as the state’s best-known congressional face has brought Wisconsin plenty of intangible attention. But House Budget Chairman Paul D. Ryan is really the state’s only personification of congressional clout. Two other Republicans in the delegation are both in their 18th terms, but neither Jim Sensenbrenner nor Tom Petri holds a gavel this time; both Wisconsin senators are first-termers and the state’s $6,500 in per capita spending is in the bottom 10.

All of which helps explain why the delegation’s clout is 29th today but was 16th four years ago, when Democrats ran both sides of the Capitol and placed then-Rep. David R. Obey in charge of House Appropriations while Sens. Russ Feingold and Herb Kohl, with 38 years’ seniority between them, wielded a combined five committee or subcommittee gavels.

Indiana has slipped 15 spots down to No. 42 — even though it is 16th in population — in no small measure because the state can no longer rely on the sway that came with Republican Richard G. Lugar’s six terms in the Senate and the power that Mike Pence (who’s now governor) wielded four years ago as House Republican Conference chairman, then the No. 3 minority leadership job. Today, federal spending is down in Indiana and its nine-member House delegation commands just two seats on exclusive committees: veteran Democrat Peter J. Visclosky on Appropriations and junior Republican Todd Young on Ways and Means.

Little West Virginia punched the highest above its weight back in the spring of 2009, when the legendary Robert C. Byrd was still openly seeking as much federal largess for his state as possible from the top seat on Senate Appropriations. Its clout ranked 12th then. Now, three years after Byrd’s death, it has dropped to No. 25, which still isn’t too shabby for a state of fewer than 1.9 million people. Sen. Jay Rockefeller’s varied committee positions of power and his three decades of Senate seniority are a big reason why, and the state looks sure to see another big drop when he retires next year.

Missouri’s clout ranking dropped a dozen notches in the past four years, to No. 30, in part because it lost a House seat in reapportionment, in part because House Armed Services Chairman Ike Skelton was swept out in the 2010 GOP tide, and in part because Roy Blunt gave up his considerable influence in the House GOP leadership to start from scratch again in the Senate, where he took the place of the pretty-powerful-after-24-years Christopher S. Bond.

And which have been the most profound gainers among the state delegations during the same time?

After Louisiana, the biggest “with a bullet” designation goes to minuscule Delaware. In 2009 it ranked 49th — its venerable senior senator, Joseph R. Biden Jr., having just decamped for the vice president’s office and leaving former aide Ted Kaufman as his appointed place holder, and with out-of-power Republican Michael N. Castle in the solitary House seat. The new Clout Index elevates the state 22 positions, to No. 27, thanks to the Senate Homeland Security chairmanship just awarded to Democrat Thomas R. Carper, and an eighth-best $12,750 in per capita spending two years ago, the most recent data provided by the Census Bureau.

Advancing 20 notches in just four years, all the way to No. 12, is South Carolina. The big move is mostly on the strength of the level of federal spending there, which at $17,000 for every person is exceeded by only three other states. But it’s also because the relatively junior delegation is dominated by majority Republicans, one of whom occupies a new seat created only this year. At least until Tuesday’s special election, the only Democratic House member is James E. Clyburn, who carries considerable clout of his own as assistant minority leader and arguably the most powerful African-American in Congress.

Oregon is the final state to move more than 10 clicks one way or the other, advancing 13 positions to No. 26, which puts the delegation’s potential clout right about where the state ranks in the population table. The big gain in the past four years is because Democrat Ron Wyden has become chairman of Senate Energy and Natural Resources and Republican Greg Walden has taken the chairmanship of the House Republican campaign organization.

Correction May 7, 12:48 p.m.

An earlier version of this post implied that Reps. Peter J. Visclosky and Todd Young are from Wisconsin. They represent Indiana.